The Endocrine System

Humans, like all mammals, are composed of millions of cells, collections of which are highly specialised. We must live, grow, sustain ourselves and reproduce to continue the species. Reproduction itself is a complex process leading to conception, cell proliferation, and the development of a new male or female baby. The new human must grow and in turn, perhaps, have his or her own child.

The endocrine system influences or controls almost all of these stages in our development in some way or another. Hormones are the complex molecules that the endocrine system uses to manage all of these things.

Hormones are involved in all physiological functions such as: muscle activity, digestion, respiration, how we perceive the outside world through all our senses, thought, mood, behaviour - the list could go on.

The coordination, integration, regulation, stimulation and suppression of all aspects of the endocrine system has to be done in such a way that we remain feeling entirely healthy at all times in our changing environment and with changing demands on us at different times. This is an amazingly complex task requiring checks and balances to be in place at all times. It is not surprising that this wonderfully complex and critical system can occasionally break down.

The endocrine glands are glands that manufacture the hormones and secrete them directly into the bloodstream.

Hormones are secreted directly into the bloodstream in order that they can travel around the body and act as chemical messengers that instruct other glands, organs or collections of cells on what they should be doing.

The main endocrine glands include:

  • The pineal gland
  • The hypothalamus
  • The pituitary gland
  • The parathyroid glands
  • The thyroid gland
  • The pancreas
  • The adrenal glands
  • The ovaries in women and the testes in men

It used to be thought that the only glands that secreted hormones were those listed above. However, it is now clear, through medical research, that there are many collections of cells throughout the body that generate and secrete an enormous variety of hormones. These other sites and hormones are not directly relevant to thyroid hormone issues so they will not be discussed on this website unless some specific issue prompts their inclusion.